RFR (L) 8171392 Move Klass pointers outside of ConstantPool entries so ConstantPool can be read-only

Ioi Lam ioi.lam at oracle.com
Tue Apr 11 06:26:35 UTC 2017

Hi,please review the following change


   + ConstantPool::klass_at(i) finds the Klass from the i-th slot of 
   + When a klass is resolved, the ConstantPool is modified to store the 
Klass pointer.

   + ConstantPool::klass_at(i) finds the at this->_resolved_klasses->at(i)
   + When a klass is resolved, _resolved_klasses->at(i) is modified.

   In addition:
     + I moved _resolved_references and _reference_map from ConstantPool
       to ConstantPoolCache.
     + Now _flags is no longer modified for shared ConstantPools.

   As a result, none of the fields in shared ConstantPools are modified 
at run time,
   so we can move them into the RO region in the CDS archive.

   - Benchmark results show no performance regression, despite the extra 
level of
     indirection, which has a negligible overhead for the interpreter.
   - RBT testing for tier2 and tier3.

   - I have tested only the Oracle-support ports. For the aarch64, ppc 
and s390 ports,
     I have added some code without testing (it's probably incomplete)

   - Port owners, please check if my patch work for you, and I can 
incorporate your
     changes in my push. Alternatively, you can wait for my push and 
provide fixes
     (if necessary) in a new changeset, and I will be happy to sponsor it.

- Ioi

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